Regenerative gas refrigerating machines are used to generate cryogenic temperatures. They operate according to the principle of a thermodynamic cyclic process. The working gas exchanges heat between the two temperature levels in a regenerator (FIG. 1). The parameters for the refrigerating capacity and consequently for the maximum attainable final temperature are the gas mass participating in one cyclic process and the number of cyclic processes run through per unit time.
To reach the most constant final temperature possible with such a gas refrigerating machine for certain applications, it has been suggested that the final temperature be limited by electrically controlling the input power. This possibility of control is relatively expensive and prone to malfunction.